Background: Circle contact lenses, also known as color contact lenses and big eye contact lenses, are a type of cosmetic contact lens. It is not generally known that a circle contact lens usually contains iron oxide and other metals, which means their use during magnetic resonance imaging (MRI) is a potential hazard. Case presentation: We present a rare case of incidental discovery of circle contact lenses by MRI and MRI images of circle lenses in vitro. Conclusions: Circle contact lenses usually contain iron oxide, which is a known source of susceptibility artifact on MRI. Not only radiologists and radiographers but also referring physicians should be familiar with the imaging findings and potential risk of scanning circle contact lenses by MRI.